These experiments are designd to study the mechanism of excitation of the auditory nerve fibers in the cochlea, particularly to ascertain the excitatory role of the cochlear microphonics (CM) and summting potentials (SP). This will be accomplished by simultaneously recording the cochlear potentials and the neural responses of single fibers originating in the turn of the guinea pig cochlea where the cochlear potentials are measured. The potentials will be modified by the application of extrinsic current or ethacrynic acid and the changes in the endocochlear potentials, CM and SP will be quantitatively compared with the changes in the neural response. Kanamycin-treated guinea pigs will be used to investigate the role of the inner and outer hair cells. Comparative studies will be made on the function of hair cells in the lateral-line orgaa of the African clawed toad Xenopus laevis. The effects of electric potentials upon spontaneous and evoked activity an the role of the cupula will be investigated. Bibliographic references: Strelioff, D., Honrubia, V.: Effects of electrical potentals upon hair-cell function. Meeting of the Acoustical Society of America, St. Louis, Nov. 1974. J. Acoust. Soc. Amer. 56, Suppl., S10, Fal 1974. Honrubia, V., Strelioff, D., Sitko, S.: Changes in scala media potentials produced by ethacrynic acid. Meeting of the Acoustical Society of America, St. Louis, Nov. 1974. J. Acoust. Soc. Amer. 56, Suppl., Sil, Fall 1974.